Refrigerant flow control for improving low capacity efficiency



l 25, 1967 E. LE CHIEN ETAL 3,315,486

REFRIGERANT FLOW CONTROL FOR IMPROVING- LOW CAPACITY EFFICIENCY FiledFeb. 16, 1966 FIGZ FIG 3 INVENTORS. ELLIS L. LE CHIEN. DONALD R. CHECK.

ATTORNEY.

YBY

O O O O O O O O O O 0 O O O O O O O O O O O O 000 O O O O O O UnitedStates Patent 3,315,486 REFRIGERANT FLOW CONTROL FOR IMPROV- ING LOWCAPACITY EFFICIENCY Ellis L. Le Chien, Syracuse, N.Y., and Donald R.Check,

Minneapolis, Minn., assignors to Carrier Corporation,

Syracuse, N. a corporation of Delaware Filed Feb. 16, 1966, Ser. No.527,870 2 Claims. (Cl. 62218) ABSTRACT on THE DISCLOSURE A centrifugalrefrigeration machine having a tube bundle in the evaporator sectionthereof for passage therethrough of the medium to be cooled. A floatcontrolled metering valve, provided to regulate flow of refrigerantbetween the condenser and evaporator, is operably connected to asolenoid which holds the valve open under low load conditions to passgaseous refrigerant to the evaporator to cause agitation of liquidrefrigerant therein. The liquid agitation insures wetting of theevaporator tubes by liquid refrigerant for maximum evaporatorefficiency.

This invention relates broadly to a refrigeration machine. Moreparticularly, this invention relates to control of refrigerant flow in arefrigeration machine. Still more particularly, this invention relatesto a liquid refrigerant metering device particularly equipped to pass amixture of liquid and gaseous refrigerant to the evaporator of arefrigeration machine at low load conditions to improve the efiiciencyof the evaporator at low load.

In high tonnage refrigeration machines, a compressor is arranged toextract gaseous refrigerant from an evaporator, compress therefrigerant, and pump it to a condenser where it is cooled andcondensed. In communication with the condenser, there is normallyprovided a receiver for collecting liquid refrigerant formed in thecondenser prior to its passage to the evaporator. The receiver usuallycontains refrigerant both in the liquid and gaseous phases and flow fromthe receiver is regulated by a float operated valve mechanism.

Under normal operating conditions, the level of the liquid refrigerantcollected in the receiver is a function of the pressure differencebetween the high pressure side of the machine and the low pressure sideof the machine and the load on the machine, it being understood thecondenser and receiver are disposed in the high pressure side and theevaporator in the low pressure side of the machine. Refrigerant flowfrom the high side to the evaporator occurs in an amount related to theloading on the machine and automatic controls such as suction guidevanesare provided for the purpose of maintaining flow rates corresponding tomachine loading. Float operated valve assemblies are designed to pass apredetermined amount of refrigerant in accordance with the level ofrefrigerant collected to maintain a liquid seal in the receiver.

The liquid from the receiver is passed through the float valve to theevaporator. The evaporator contains a multiplicity of tubes usuallyreferred to as a tube bundle through which the medium to be cooled bythe machine is passed in heat transfer relation with the refrigerant inthe evaporator. Under normal operating conditions, the heat supplied tothe refrigerant from the medium being cooled is suificient to cause theliquid refrigerant in the evaporator to boil vigorously. The boilingrefrigerant thus wets all the tubes in the evaporator, providing optimumheat transfer between the medium and the refrigerant. However at lowloads, a relatively small quantity of heat is given off by the medium.The refrigerant, under these conditions, does not boil vigorously enoughto wet all the tubes particularly those in the upper rows of the bundle,causing the efliciency of the evaporator to decrease. Therefore, tomaintain evaporator efliciency at low load, the liquid refrigeranttherein must be agitated. To accomplish this, a portion of the highpressure gaseous refrigerant from the condenser is passed through thepool of liquid refrigerant in the evaporator.

The chief object of this invention is to provide a simplifiedrefrigerant flow control for passing both liquid and gaseous refrigerantto the evaporator under certain operating conditions. It is anadditional object of this invention to provide a refrigerant controldevice which will maintain a liquid seal in the condenser under normaloperating conditions. A further object of this invention is to provide acontrol for passing liquid and gaseous refrigerant to the evaporator toprovide agitation of the liquid refrigerant therein under low loadconditions.

These objects are attained by providing a float valve actuator tomaintain the float valve open a desired amount at low load conditionsregardless of the liquid level in the receiver. The actuator is operablein response to an operating characteristic of the refrigeration machineindicating low load such as guide vane position.

Other objects and features of this invention will be apparent upon aconsideration of the ensuing specification and drawings in which:

FIGURE 1 is a somewhat schematic view of a refrigeration machine,wherein the evaporator-condenser section is shown in sectionalelevation, incorporating a control mechanism illustrating the invention.

FIGURE 2 is a fragmentary view of the receiver of a refrigerationmachine illustrating a float valve and float valve actuator.

FIGURE 3 is a sectional view of the receiver portion of therefrigeration machine illustrating a second embodiment of our invention.

Referring more particularly to the drawing there is shown a centrifugalrefrigeration machine 1 for cooling a large quantity of water or brine.Refrigeration machines of this type are employed to cool water or brineflowing within a closed circuit forming a part of an air conditioninginstallation. The machine 1, having a refrigerant motor compressor 2,includes shell 3 for housing the heat transfer units (evaporator andcondenser) associated with the machine. The shell 3 has a partition 4therein for separating the high pressure condenser section 5 from thelow pressure evaporator section 6. Tube bundle 7 in evaporator section 6is provided for passing water to be chilled therethrough.

Refrigerant receiver, or float box 8, is provided for receiving gaseousand liquid refrigerant from the condenser through opening 9communicating therewith. Float valve assembly 10 in float box 8 isprovided for metering refrigerant from the float box to the evaporatorsection 6 through passageway 9'. The float valve assembly 10 comprisesfioat ball 11, float arm 12, and throttle plates 13 rigidly connected toarm 12. The float valve assembly is pivoted on pin 14 mounted in thesides of an opening 14' formed in the receiver. Actuator assembly 15consisting of solenoid 16 and actuator arm 17 is provided to hold floatvalve assembly 10 open when solenoid 16 is activated in a manner to belater explained.

FIGURE 3, illustrating a second embodiment of our invention, has anactuator assembly 18 consisting of solenoid 19 and actuator arm 20 tohold float valve assembly 10 open when solenoid 19 is activated. In thisembodiment, the solenoid is located outside the receiver.

Considering the operation of the refrigerant control device illustratedin FIGURES 1 and 2, under normal operating conditions, float valveassembly 10 will maintain a constant liquid refrigerant level in floatbox 8. Under low load conditions, liquid refrigerant level will tend tobuild up in the evaporator. However, float valve assembly will stilloperate to maintain a relatively constant liquid level in the float box8. In order to do so, float valve assembly 10 will be substantiallyclosed and flow of refrigerant to the evaporator will be minimal. Underthese conditions, the heat given off by the water being chilled will beinsufiicient to boil the collected refrigerant in the evaporator. Theupper tubes of the tube bundle will not be wetted by the refrigerant andthe capacity of the refrigeration machine will decrease.

To maintain the efliciency of the refrigeration machine at a high level,it is desirable to pass both liquid and gaseous refrigerant to theevaporator to cause agitation of the liquid therein to wet all thetubes'of the tube bundle. To accomplish this, the float valve assembly10 is opened to allow all of the liquid collected therein and gaseousrefrigerant to pass through passageway 9 into the evaporator. Byactuating solenoid 16 in response to a machine operating characteristicindicative of low load such as compressor inlet guide vane position,float valve assembly 10 will be held open thereby breaking the liquidseal in float box 8 allowing liquid and gaseous refrigerant to passtherethrough to agitate the collected liquid refrigerant in evaporator6. 7

While we have described a preferred embodiment of our invention, it isto be understood that the invention is not limited thereto since it maybe otherwise embodied within the scope of the following claims.

We claim:

1. In a centrifugal refrigeration system, the combination of a highpressure side including a centrifugal compressor and a condenser;

a low pressure side including an evaporator having a tube bundl therein;7

a refrigerant metering device comprising afloat valve tor to maintain aconstant liquid level in the'high pressure side under normal operatingconditions; and p an actuating assembly for actuating said float valve,said assembly being responsive to an operating characteristic of thesystem at low load to hold said valve open irrespective of therefrigerant level in the high pressure side to pass gaseous refrigerantfrom the high pressure side to the, evaporator to agitate liquidrefrigerant in the evaporator thereby wetting sub-.

stantially all the tubes of the bundle with liquid refrigerant toincrease evaporator efliciency under low load conditions. 2. Acentrifugal refrigeration system according 'to claim 1 wherein saidactuator assembly comprises:

an actuator arm operably associated with said float valve to hold saidfloat valve open when said arm is retracted, and

a solenoid operably connected to said actuator arm to retract said armwhen said solenoid is energized.

References Cited by the Examiner UNITED STATES PATENTS 2,068,249 1/ 1937Terry 62218 2,581,330 1/1952 Patterson 62-509 2,667,756 2/1954 Atchison62-174 2,715,317 8/1955 Rhodes 62149 2,871,673 2/1959 Richards et a1.62509 2,921,446 1/ 1960 Zulinke 62-1 17 LLOYD L. KING, Primary Examiner.

1. IN A CENTRIFUGAL REFRIGERATION SYSTEM, THE COMBINATION OF A HIGHPRESSURE SIDE INCLUDING A CENTRIFUGAL COMPRESSOR AND A CONDENSER; A LOWPRESSURE SIDE INCLUDING AN EVAPORATOR HAVING A TUBE BUNDLE THEREIN; AREFRIGERANT METERING DEVICE COMPRISING A FLOAT VALVE DISPOSED IN THEHIGH PRESSURE SIDE OF THE SYSTEM TO METER PASSAGE OF REFRIGERANT FROMTHE CONDENSER TO THE LOW PRESSURE SIDE, SAID FLOAT VALVE BEING OPERABLEIN RESPONSE TO LIQUID REFRIGERANT LEVEL IN THE HIGH PRESSURE SIDE TOPASS REFRIGERANT TO THE EVAPORATOR TO MAINTAIN A CONSTANT LIQUID LEVELIN THE HIGH PRESSURE SIDE UNDER NORMAL OPERATING CONDITIONS; AND ANACTUATING ASSEMBLY FOR ACTUATING SAID FLOAT VALVE, SAID ASSEMBLY BEINGRESPONSIVE TO AN OPERATING CHARACTERISTIC OF THE SYSTEM AT LOW LOAD TOHOLD SAID VALVE OPEN IRRESPECTIVE OF THE REFRIGERANT LEVEL IN THE HIGHPRESSURE SIDE TO PASS GASEOUS REFRIGERANT FROM THE HIGH PRESSURE SIDE TOTHE EVAPORATOR TO AGITATE LIQUID REFRIGERANT IN THE EVAPORATOR THEREBYWETTING SUBSTANTIALLY ALL THE TUBES OF THE BUNDLE WITTH LIQUIDREFRIGERANT TO INCREASE EVAPORATOR EFFICIENCY UNDER LOW LOAD CONDITIONS.